#include <iostream>
#include <fstream>
#include <deque>
using namespace std;
const int nmax=100005;
deque<int> d;
int c[nmax];
int n,s,t,p,i;
long long tot;
int main()
{
    ifstream f("branza.in");
    ofstream g("branza.out");
    f>>n>>s>>t;
    for(i=1;i<=n;i++)
    {
        f>>c[i]>>p;
        c[i]=c[i]-i*s;
        if((!d.empty())&i-d.front()>t)
            d.pop_front();
        while((!d.empty())&&c[i]<c[d.back()])
            d.pop_back();
        d.push_back(i);
        tot+=1LL*(c[d.front()]+i*s)*p;
    }
    g<<tot;
    return 0;
}